In light of the thousands of lawsuits pending against Johnson and Johnson and talc-supplier Imerys claiming that prolonged genital use of talc-containing products caused women’s ovarian cancer, Law360 had experts explain some of the details of where talc science is today.
Epidemiology, the discipline that is most often used to try to prove that a substance causes a disease, is the study and analysis of the patterns, causes, and effects of health and disease conditions in defined populations. There are several study designs.
Randomized clinical trial
The “best” study, a randomized clinical trial, which is used to study drugs, isn’t ever going to be used to study talc. It involves exposing participants to the substance and comparing the results to a control. However, in the case of a substance like talc, which has no health benefit to participants and could cause cancer, this type of study is not worth the risk.
Retrospective/case control studies
Retrospective or case control studies are a safer, easier, cheaper and common study design, however they face issues such as recall bias, because they rely on participants’ memory. A group of people who have a disease are identified and then scientists question them about their exposure to possible risk factors for the disease.
Ten case control studies have been conducted examining the talc ovarian cancer link. Law360 reports that according to Dr. Adetunji Toriola, an epidemiologist and assistant professor at the Washington University School of Medicine in St. Louis “their ‘overwhelming conclusion’ is that women who use talcum powder on their genital area are more likely to develop ovarian cancer” and the association is consistent from studies with small sample sizes to those with thousands of participants.
Dr. Toriola explains a statistic used by epidemiologists called odds ratios, saying that courts have begun looking for an odds ratio threshold of 2.0 when determining if a substance caused a disease. The ratio of 2.0 indicates that a person’s chance of developing the disease was doubled by their exposure to the risk factor. However, Dr. Toriola claims that any number above 1 indicates a connection, with 1.5 representing a significant increase risk, saying that the threshold for saying a risk factor causes a disease is not clear in epidemiology. “Using a threshold of two as a cutoff is very arbitrary,” he said.
Evidence analyzing multiple talc studies shows an odds ratio between 1.2 and 1.3 overall for ovarian cancer and genital talc use. Dr. Toriola noted that the odds ratio for breast cancer and alcohol is between 1.15 and 1.3 and it is widely accepted that it increases a woman’s risk, noting the World Health Organization acknowledges the risk.
Another type of study is a cohort study, which tracks a group of healthy people’s risk factors and years later analyses the same group to see what diseases manifested during the interim, looking back to see how exposure to the risk factors might have influenced the diseases that participants developed. Several large cohort studies looking at talc have not shown a statistically significant link to ovarian cancer. However, ovarian cancer, as a very rare disease, might require a larger sample to confirm the results that the case control studies were consistently finding, Dr. Toriola suggested.
Expert epidemiologist Dr. Toriola and Dr. Joshua Muscat, a professor in the Department of Public Health at Penn State, who co-authored “Perineal Talc Use and Ovarian Cancer: A Critical Review” in the in European Journal of Cancer, discussed the studies that have shown a biological explanation for how talc might be causing ovarian cancer.
Inflammation in the ovaries and fallopian tubes can be caused by talc particles, and that inflammation is independently linked to higher rates of ovarian cancer. Dr. Muscat questioned how much talc is reaching the ovaries, saying that pathologists are finding talc particles in the ovarian tissue of women with ovarian cancer, but often “very few” particles.
“The scientific evidence has split both scientists and courts,” Law360 reports.
Talc litigation would benefit from more research, specifically cohort studies designed to study clarify this important issue.
“Even the Supreme Court has said arguably there are no certainties in science because it’s an evolving process,” said Jean Eggen, distinguished emeritus professor at Widener University Delaware Law School. “The law doesn’t look at things like this at all. The law says, ‘We have to decide what’s true right now,’” she said.